Meaning

noun a tenth part; one part in ten equal parts

noun position ten in a countable series of things

adjective coming next after the ninth and just before the eleventh in position

originFrom Middle English tenth, tenthe. Old English had tēoþa (origin of Modern English tithe), but the force of analogy to the cardinal number "ten" caused Middle English speakers to recreate the regular ordinal and re-insert the nasal consonant. Ultimately from Proto-Germanic *tehundô. Equivalent to ten (numeral) + -th (suffix forming ordinals).

Etymology from Wiktionary, CC BY-SA 3.0